Performance Trends, Inc.

Producing Quality Computer Tools for Racers and Engine Builders since 1986

Wide Band UEGO A/F (lambda) Sensors

Affordable, Rugged True A/F Sensors and Controller for Accurate Engine Tuning and Troubleshooting on Dyno or In Vehicle

Our DT2-AFG (system with gauge) and DT3-AF1 (system without gauge) A/F sensor/controller systems uses a Bosch 5 wire oxygen sensor to accurately measure A/F ratio, or Lambda, over a wide range of values from approximately .6 to 1.3 Lambda.  For typical gasoline, this is from approximately 9.5:1 rich up to 19:1 lean.  for info on our DT2-AFR Remote Sampling system or  for info on our DT2-AFRM Mini Remote Sampling system for small engines and chassis dynos.

New (as of Dec 2015) A/F Checker
A-F Checker production clean bkgd.jpg (214791 bytes)  click image to enlarge for info on our A/F Checker to verify the accuracy of your A/F Measurements. 

New (as of July 2010) Very Affordable DT3-AF1 Single A/F channel

Single Channel UEGO AF DT3-AF1.jpg (91851 bytes) click image to enlarge


DT2-AFG A/F Gauge, requires no computer or data logger 

Click here for DT2-AFG Features

Click here for info on FREE data logging software

for notes on Sensor Life.

for prices. 

for a table comparing systems.

Our systems come with Molex connectors for plugging directly into our DataMite data loggers.  For vehicle installations, the user must provide 9-18 VDC power (typically from the vehicle's battery).  For dyno installations, we recommend the DT2-AFGP (gauge) and DT3-AF1P (without gauge) part numbers which come with AC power supplies, as shown as the option in the figure above.

Exhaust Oxygen Sensor Theory

Typical production car O2 sensors rely on “nernst cell” technology, commonly called “Narrow Band”, “2 wire”, “4 wire” and sometimes erroneously described as “Wide Band”. This is a very cost effective method that outputs a voltage based on the oxygen content of the gas being sampled. It is accurate in the region surrounding stoichiometric operation and leaner. Unfortunately, in the rich region where high performance engines usually operate, their accuracy and repeatability is virtually non-existent.


Characteristic curve of an nernst cell type O2 Sensor

The rich region output of a common O2 sensor is very temperature dependant, which renders it useless if an accuracy greater than 1.5:1 AFR is desired. This is immediately obvious given the fact that a single output voltage actually represents wildly different AFR’s depending on the unregulated and unmeasured sensor temperature. These sensors were designed for operating closed loop around the stoichiometric AFR (14.64 for gasoline), and for performance tuning they are useless.

The heart of the Performance Trends Wideband controller is the Bosch LSU4.2 Universal Exhaust Gas Oxygen (UEGO) sensor. This type of sensor is commonly referred to as “laboratory grade” and works on a different principle than the normal oxygen sensor you would find in your car. Its unique design makes precision AFR measurement possible over the entire operating range.

UEGO type sensors use a “current pump” within the sensor itself to determine the actual oxygen concentration within the sensing element or, lacking any O2, it determines the amount of oxygen required to regain stoichiometric operation. The output is in the form of a very small current which varies depending on the air-fuel ratio. This is completely different from a normal oxygen sensor (1, 2 and 4 wire types) which directly output a voltage. The UEGO design allows measurement of the exact air fuel ratio over the entire operating range.

Each Performance Trends UEGO sensor is individually calibrated and a resistor integral to the connector body is laser trimmed with this value. This process replaces the traditional “free air” calibration procedure when changing sensors and implements a sensor specific calibration for unparalleled accuracy.

UEGO sensors laser etched calibration resistor


Oxygen Sensor Placement

A weld-in M18 X 1.5 boss is supplied for sensor installation. Mount the O2 in the Exhaust System at least 18 inches downstream from the exhaust port as the extreme temperatures of the exhaust can harm the sensor. The sensors internal heater will warm the sensor to the optimum operating temperature. If available, the factory O2 sensor location is usually preferable. On turbocharged engines the UEGO sensor must be installed after the Turbo Charger, if not, the pressure differential will greatly effect the accuracy of the unit. In applications with a catalytic converter, the UEGO sensor must be mounted BEFORE the converter. In applications with an auxiliary air pump, the UEGO sensor must be mounted BEFORE the pump input to the exhaust stream. Installation angle should be inclined at least 10° towards horizontal (electrical connection upwards, see diagram) which prevents the collection of liquids between sensor housing and sensor element during the cold start phase.  

Minimum mounting angle for the UEGO Sensor

Notes on the Sensor:
  • You can typically tell if a sensor is starting to fail if it is very slow to respond to changes in A/F, like from blipping the throttle, or slow to show proper signals during warm-up (system power on but engine not running).  The response will continue to slow until finally there is no response from the sensor.  Running the sensor in "clean" exhaust for a while can partially restore a sensor.  See Note below about "cleaning".

  • The sensor contains a ceramic module and should not be subject to mechanical or thermal shock or it may be damaged.  Thermal shock would occur if liquid drops of water were to contact the sensor, like if a sampling trap for the DT2-AFR Remote sampler were to over fill.

  • The sensor is not designed for operation on leaded fuels, doing so will shorten sensor life.

  • Long term running in the rich region (Lambda < 0.95) will shorten sensor life, running very rich will dramatically reduce sensor life.

  • High exhaust temperatures (over 850 deg C, 1560 deg F) will shorten sensor life.

  • Engine oil consumption at a rate greater than 1 quart per1,000 miles will shorten sensor life.

  • Do not run the engine with the UEGO sensor installed without power applied to the controller and the sensor plugged in.

  • It may be possible to "clean" sensors if you run them in a modern, production car with good emissions, with the proper DT2-AF1, DT2-AF2 or DT2-AFG controller connected.  This must be done before the sensor has completely failed.

  • A good rule of thumb for sensor life is:  A sensor will last about as long as your spark plugs.  If your spark plugs are fouled by lead or very rich running, you sensor is likely to have failed also.


DT3-AF1 Single Channel Sensor

This is a "bare bones" A/F sensor system.  It includes 1 A/F sensor (LSU 4.2 like all our systems) and the signal conditioning to provide a 0.5 to 4.5 volt signal for a data logger.  The conditioning is molded directly into the cable.  This is our most affordable way to add a single A/F sensor to your data logger, or one sensor for each cylinder.
Single Channel UEGO AF DT3-AF1.jpg (91851 bytes)  click image to enlarge it


DT2-AFG A/F Gauge

The Wideband UEGO Gauge system displays A/F real time as a 3 digit number and on the 24 segment, analog, color coded, 270 degree sweep "needle" around the outside of the 2 inch dial.  The gauge is designed for dash mounting like most any other gauge (tachometers, oil pressure, etc).  If you want something easy to use for tuning carbs, dyno testing, EFI tuning, this is it.  And if you ever decide to get a DataMite or Black Box Data Logger, you can continue to use the DT2-AFG because it has a 0-5 volt output.  Features include:

  • Bosch 5 wire UEGO sensor, mounting hardware and all wiring included.

  • 3 digit numerical readout.

  • 24 segment, color coded sweep analog output.

  • 0-5 volt analog output compatible with most any data logger or engine controller.

  • Alternate 0-1 volt outputs to simulate the Autronic Wideband O2 Sensor calibration or standard, narrow band O2 sensors.

  • Output can be switch between A/F or Lambda.

  • Stable, accurate readings because a 5 wire, truly wide band oxygen sensor is used.

  • Serial output (RS232) for experienced computer users to read directly.

  • 12 page instruction booklet with all details about settings and output signals.

IMPORTANT:  The DT2-AFG is a complete UEGO controller contained in the gauge body itself.  It is NOT an add on to the DT2-AF1 controller.  In fact, the gauge controller has different features and different output signals.  See installation diagram below.

The DT2-AFG also comes with FREE software shown below.  for a FREE Data Logger Demo. This software lets your computer (typically a lap top computer) record the A/F from the gauge through the Blue wire, and save it for detailed analysis.  Performance Trends can add a connector and (USB adapter if necessary) to make this a plug and play installation for a small charge.  

Click here to download a demo of this software.

to go to our Demo Downloading page to download a FREE Data Logger Demo.



Comparison of Systems

The table below compares the features of the 2 systems:



Cost, as of July 2010 $299 $219

Number of Sensors   



Power Required   

1.3 amps

1.3 amps

Voltage Required   

9-18 DC *

9-18 DC *

Serial Data Output (so A/F can be recorded with free software)   



0-5 volt Analog Output   

Yes **


Linearity of 0-5 volt output   

Linear ***

Linear  ***
0-5 Volt Signal Connectors No, but can be added at additional cost No, but can be added at additional cost

0-1 volt Output for ECM   

Yes **


Harness and connector temp limit   

220 deg F / 105 deg C

220 deg F / 105 deg C

Measurement Range   

.68 to 1.26 lambda (10-18.5 A/F gas)****

.58 to 1.22 lambda (8.5-18 A/F gas)
Construction Less rugged *****  Very rugged

* Optional AC power supplies available
** DT2-AFG lets you select either a 0-5 or 0-1 volt output, but you can not have both at the same time.
*** Performance Trends' DataMite programs all have built in calibrations for all systems, so being linear or non-linear is not an issue.  However, other data loggers may not handle a non-linear sensor very well (where you need to enter a table of calibration data).  For these data loggers, the linear DT2-AFG is best.
**** The digital display shows 10-18.5 A/F, the analog sweep LEDs show from 11 to 17 A/F.
***** The DT2-AFG is a less rugged construction because of the plastic gauge readout and housing, and some smaller connectors on the back of the gauge.


DT2-AFRM Mini Remote Sampling System

The Mini Remote Sampler is similar in function as the larger DT2-AFR system described below.  It is less expensive, lighter, and smaller so it can be placed very close to the exhaust pipe.  It does not have all the options of the full DT2-AFR, but it certainly works well for many applications.

for an example of one user's installation (with pictures) and experience with the Mini Remote.


DT2-AFR Remote Sampling System

The DT2-AFR Remote Sampling System provides a pump, sampling cell and sampling probe for easy monitoring of vehicles on chassis dynos.  Simply place the probe in the exhaust pipe and you're done.  It is available in either single or dual channel models. 


The Remote Sampler is also a method that small engine tuners can use to measure A/F on their engines.  The UEGO sensor is typically too large to be mounted in the exhaust pipe of most single cylinder engines.  The remote sampler lets you pull a small sample from the exhaust without affecting the engine's performance.


A/F Checker

A-F Checker production clean bkgd.jpg (214791 bytes)  click image to enlarge for info on our A/F Checker to verify the accuracy of your A/F Measurements. 




The A/F sensors can even be used on 2 stroke engines, as shown below in the graph of results from an 85 cc 2 stroke.  The data was obtained with remote sampler fitted with a special trap for the oil aerosol developed by the dyno operator. The dyno operator says the A/F data is very valuable to track changes in tuning which has a large impact on the 2 strokes power output.  Note also how the Head temperature gets warmer as the A/F gets leaner.  We will soon be able to fit an aerosol trap to our DT2-AFR Remote Sampling System for 2 stroke engines.  (Due to the high oil consumption of 2 strokes, sensor life is reduced and some systems do not recommend use with 2 strokes.  We are still investigating the accuracy on 2 strokes and the expected life of the sensors.)


Even Alcohol Briggs & Stratton Kart motors can use the A/F Sensors with proper installation.  Below is a graph of 2 tests courtesy of Bryan Pigg of PPE Motorsports in Yazoo City, Mississippi .  He mounted his sensor in the muffler (this class required a muffler).  The restriction of the muffler better maintained the heat to the sensor, and helped prevent any leakage to allow room air get to the sensor, which makes the sensor read too lean.  The graph shows that Test 4 with an A/F in the range of 6.5:1 was too lean for this alcohol motor.  When he richened it up to around 5.8:1, he picked up torque and HP throughout the entire RPM range. 


to return to the top.

for prices.


What You Need for Software Option:

Computer with Windows 95, 98, Me, XP, 2000 or NT, Vista, Windows 7, Windows 8.  for Vista, Win 7, Win 8 tips.


To Order:

Call 248-473-9230. Visa or Mastercard accepted.